Optogenetic rescue of a developmental patterning mutant

Abstract

Animal embryos are partitioned into spatial domains by complex patterns of signaling and gene expression, yet it is still largely unknown what features of a developmental signal are essential.Part of the challenge arises because it has been impossible to "paint" arbitrary signaling patterns on an embryo to test their sufficiency. Here we demonstrate exactly this capability by combining optogenetic control of Ras/Erk signaling with the genetic loss of terminal signaling in early Drosophila embryos. Simple all-or-none light inputs at the embryonic termini were able to completely rescue normal development, generating viable larvae and fertile adults from this otherwise-lethal genetic mutant. Systematically varying illumination parameters further revealed that at least three distinct developmental programs are triggered by different cumulative doses of Erk. These results open the door to the targeted design of complex morphogenetic outcomes as well as the ability to correct patterning errors that underlie developmental defects. SummarySpatial gradients of protein activity pattern all developing embryos. But which features of these patterns are essential and which are dispensable for development? Answering this question has been deceptively difficult, due to the difficulty of shaping spatial gradients using chemical or genetic perturbations. Johnson and colleagues use optogenetics to fully restore normal embryo development with a pattern of light, opening the door to complete control over spatial organization in developing and engineered tissues.

Characteristic ERK1/2 signaling dynamics distinguishes necroptosis from apoptosis

“…This signal transmission modus resides in several features such as pulse amplitude, frequency, duration, and onset. The extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) have been early examples of how signaling dynamics features drive cellular responses, such as proliferation and differentiation (Albeck et al, 2013;Aoki et al, 2013;Johnson and Toettcher, 2019;Ryu et al, 2016). While there is compelling evidence of ERK1/2 involvement in different cell death modalities, ERK1/ 2 controversial effects made its understanding in cell death daunting.…”

Lights up on organelles: Optogenetic tools to control subcellular structure and organization

“…Titratable light‐triggered cellular adjustments are often preferable to chemically induced changes as it is challenging if not impossible to add small molecules in a pulsatile manner and, once added, these chemical effectors can diffuse away from the desired target area to cause nonspecific cellular responses (Repina, Rosenbloom, Mukherjee, Schaffer, & Kane, 2017). Optogenetic systems offer increased spatiotemporal precision as only cells or subcellular regions exposed to the appropriate wavelengths of light will be impacted (Dine, Gil, Uribe, Brangwynne, & Toettcher, 2018; Goglia & Toettcher, 2019; H. E. Johnson, Shvartsman, & Toettcher, 2019).…”

Investigating the Re-initiation of Segmentation with Temporally Restricted RNAi in Tribolium castaneum

“…For example, in a not yet peer-reviewed preprint (Johnson et al, 2019), the terminal patterning system of Drosophila, that is lost in Torso signaling mutants and results in loss of both anterior and posterior structures, was rescued by the use of an optogenetically activated Ras/Erk activity (being the intracellular signaling component of Torso signaling) (Johnson et al, 2017). This approach allowed for a more nuanced modification of Torso signaling both temporally and locally.…”